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User name M. Stevens
Log entry time 19:20:54 on July 06, 2007
Entry number 207848
keyword=Rt Q1 erratic behavior
Javier, Jack and I entered the hall to repair the erratic behavior of rt.
Q1. The behavior was repeatable; the failure mode was the power supply
not going to the correct set current, and small changes in set to current
value could elicit large responses from the power supply, and not always
in the same direction as the commanded current. For example, set to of
257A returned a ~230A current, but increasing the set to to 512A got you
less than 100A back. It appeared that the binary bits of the 16 bit DAC
were becomming corrupted, we speculated by the failure of the respective
optocouplers (1 for each bit). We changed the board that carries the
optocouplers, which is the regulation module, and the power supply
behaved normally, with an acceptable and predictable offset between the
set to and read back values. The power on (uncommanded) current spike
remains, but is only an annoyance not worth investigating at this time.
The retrograde current regulation module is on the radcon shelf in the
hall; we will retrieve it when we have a daytime access, and replace the
optocouplers.
A copy of this log entry has been emailed to: folts@jlab.org, segal@jlab.org, spiegel@jlab.org, fansler@jlab.org